A comparison of soft X‐ray contact microscopy with light and electron microscopy for the study of algal cell ultrastructure

Abstract

SUMMARY Images of filamentous and unicellular algae have been obtained by soft X‐ray (wavelength 2.05‐4.4 nm) contact microscopy (SXCM), using synchrotron radiation, and the images obtained compared to those obtained by scanning and transmission electron microscopy. After chemical development to leave areas corresponding to high X‐ray absorbance by the specimen the photoresists were examined by SEM. In two algae (Anabaena and Trebouxia) cytoplasmic detail, including photosynthetic lamellae, chloroplasts, nuclei and mitochondria, were identified. In a third alga (Cyanidium) the SXCM image revealed little internal detail due to the uniformly high X‐ray absorption by the cells. The successful imaging of whole cells by SXCM is discussed in relation to conventional TEM and the future possibilities for SXCM are outlined.

Microradiography as a tool to detect heavy metal uptake in plants for phytoremediation applications

“…Fletcher et al, 1992;Ford et al, 1991;Panessa et al, 1981;Panessa-Warren et al, 1989Stead et al, 1988Stead et al, , 1992. This aim has created the soft-X-ray microscopy (i.e., the observation of individual cells or a few cells under low energy X-rays) and microradiography (i.e., the observation of small insects or plants generally imaged on a high-resolution photographic film), which were introduced for imaging the internal structure of cells and small biological samples in their normal living state.…”

“…In this region, the absorption of carbon is $10 times that of water. Hence, using X-rays in this range allows living biological specimens to be imaged with good contrast in a natural aqueous environment (Stead et al, 1988Albertano et al, 1997a).…”

“…During the last 10 y, soft-X-rays produced by laser plasmas have been widely used for the imaging tech-nique called the ''contact mode'' (SXCM), which places the sample in contact with a photosensitive plate, typically a PMMA (poly methyl methacrylate) photoresist for standard radiography (Albertano et al, 1997a(Albertano et al, , 1997bBollanti et al, 1995Bollanti et al, , 1996Bollanti et al, , 1998Conti et al, 1997;Cotton et al, 1995;Fletcher et al, 1992;Ford et al, 1991;Stead et al, 1988).…”

Compact water‐window transmission X‐ray microscopy

“…Wolter‐type objectives) have a larger collection efficiency than the zone‐plate systems discussed below but generally exhibit a resolution much lower than optical microscopes (Aoki et al ., 1998). Lensless imaging with laser‐plasma sources is performed with contact microscopy, although this technique involves a more complicated development and read‐out process, and it is difficult to obtain high resolution for thick samples (Stead et al ., 1988).…”

X‐ray contact microscopy using an excimer laser plasma source with different target materials and laser pulse durations

“…In this region the absorption of carbon is Ϸ10 times that of oxygen (and hence water). Using X-rays in this range allows living biological specimens in be imaged with good contrast in a natural aqueous environment (Stead et al, 1988;Ford, 1991;Fletcher et al, 1992).…”